1. Field of the Invention
The present invention relates to a droplet ejecting apparatus including a head unit which ejects droplets by driving of an actuator. In particular, the present invention is suitable for a droplet ejecting apparatus in which the head unit is mounted on a head holder via a reinforcing plate.
2. Description of the Related Art
There is conventionally known an ink-jet recording apparatus, as a droplet ejecting apparatus of the above-described type, in which a recording operation is performed on a recording medium with ink droplets ejected by a head unit that is reciprocated while being opposed to the recording medium. The head unit is attached to a reinforcing plate as disclosed by Japanese Patent Application No. 2005-161761, and is mounted as a unit with the reinforcing plate on a head holder. FIG. 11 is an explanatory view of the head unit and the reinforcing plate provided on the conventional ink-jet recording apparatus described above.
The head unit 30 includes a cavity unit 50 in which ink flow channels are formed, and a piezoelectric actuator 40 bonded to an upper surface of the cavity unit 50. Ink supply holes 31a, 31b, 31c, 31d for supplying inks to the ink flow channels are formed in the head unit 30. In a lower surface of the head unit 30, there are arranged a plurality of nozzle rows in each of which a plurality of nozzles that eject ink droplets are arranged. The cavity unit 50 is constituted by eight plate members stacked on each other. The plate members are adhered to each other with an adhesive (not shown).
The head unit 30 is fixed to the head holder (indicated at “9” in FIG. 3) via the reinforcing plate 60. The reinforcing plate 60 is wider than the head unit 30. The reinforcing plate 60 has an opening 60e for exposing the piezoelectric actuator 40 in a state in which the reinforcing plate 60 is adhered to the head unit 30. Reference numerals 60a, 60b, 60c, 60d indicate ink supply holes for supplying the inks to the respective ink supply holes 31a-31d of the head unit 30. The reinforcing plate 60 is adhered to the head unit 30 with a thermoplastic adhesive sheet 2. The adhesive sheet 2 has a plan-view shape corresponding to that of the cavity unit 50.
A high strength of adhesion is required when the reinforcing plate 60 is adhered to the head unit 30 with the adhesive sheet 2. Thus, a heavy load and enough heat are given between the reinforcing plate 60 and the head unit 30. As a result, the adhesive sheet 2 interposed between the reinforcing plate 60 and the head unit 30 is pressed and thinned, which leads to the high strength of adhesion and enhancement of a rigidity of the head unit 30.